We have measured spectral albedo, as well as ancillary parameters, of
seasonal European Arctic snow at Sodankylä, Finland (67°22' N, 26°39' E).
The springtime intensive melt period was observed during the Snow
Reflectance Transition Experiment (SNORTEX) in April 2009. The upwelling
and downwelling spectral irradiance, measured at 290–550 nm with a double
monochromator spectroradiometer, revealed albedo values of ~0.5–0.7
for the ultraviolet and visible range, both under clear sky and
variable cloudiness. During the most intensive snowmelt period of four
days, albedo decreased from 0.65 to 0.45 at 330 nm, and from 0.72 to 0.53 at
450 nm. In the literature, the UV and VIS albedo for clean snow are
~0.97–0.99, consistent with the extremely small absorption
coefficient of ice in this spectral region. Our low albedo values were
supported by two independent simultaneous broadband albedo measurements, and
simulated albedo data. We explain the low albedo values to be due to (i)
large snow grain sizes up to ~3 mm in diameter; (ii) meltwater surrounding the grains and increasing the effective grain size; (iii)
absorption caused by impurities in the snow, with concentration of elemental
carbon (black carbon) in snow of 87 ppb, and organic carbon 2894 ppb, at the
time of albedo measurements. The high concentrations of carbon, detected by
the thermal–optical method, were due to air masses originating from the Kola
Peninsula, Russia, where mining and refining industries are located.